1. Field of the Invention
The present disclosure relates to an abnormality determining apparatus for an air-fuel ratio sensor.
2. Discussion of the Background
Conventionally, for an abnormality determining device for an air-fuel ratio sensor of this type, there is known such as that disclosed in Japanese Unexamined Patent Application Publication No. 2003-020989, for example. With this abnormality determining device, attention is given to the fact that in the event that the air-fuel ratio sensor is in an abnormal state due to deterioration over time or the like, the output of the air-fuel ratio sensor obtained when restoring fuel supply after ending fuel cutoff operations of an internal combustion engine changes more gradually as compared to a case where there is no abnormality, and accordingly abnormality of the air-fuel ratio sensor is determined as follows. First, the maximum value in the amount of change of the output of the air-fuel ratio sensor obtained from restoration of fuel supply till stabilization of the output of the air-fuel ratio sensor is calculated (hereinafter also referred to as “output change maximum value”). Next, in the event that the calculated output change maximum value is smaller than a predetermined determination reference value, the air-fuel ratio sensor is determined to be in an abnormal state.